JPH0646571A - Initial charge circuit of voltage type inverter - Google Patents

Abstract

PURPOSE:To reduce the cost of a charging circuit and shorten the charge time to a smoothing circuit, concerning the initial charge of a voltage type inverter device high in circuit voltage. CONSTITUTION:This circuit has two insulating transformers 7 and 9 the primary windings of which are connected in series, and a current limiting resistor 6 is constituted on the primary side of one transformer, and a rectifier 8 for charge is connected to the secondary side of the other transformer 7, whereby a smoothing capacitor 2 is supplied with power for charge of a low current at low voltage at the initial stage of the charge of the rectifier 8 for charge. Hereby, for the current limiting circuit for a charge circuit, the one for low voltage will do, so an inexpensive device which can suppress the peak power of a diode, a transformer, etc., and standardize the circuit design, can be oftained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a smoothing capacitor initial charging circuit in a voltage source inverter having a high circuit voltage.

[0002]

2. Description of the Related Art FIG. 3 shows, for example, "MELTRAC-200K shown in Mitsubishi Electric general-purpose inverter catalog P6".
It is a circuit diagram which shows the conventional voltage type | formula inverter apparatus described in 1. In the figure, 1 is a rectifier for main power supplies, 2 is a smoothing capacitor, 3 is an inverter device, 4 is a load device. Reference numeral 6 is a limiting resistor for suppressing an inrush current from flowing into the smoothing capacitor 2 during initial charging, and 7 is an electromagnetic switch for flowing a main current during steady operation.

Next, the operation will be described. The inverter device 3 is a voltage source inverter configured to apply a DC voltage smoothed by the smoothing capacitor 2 as a power source to an AC voltage having a variable voltage and a variable frequency to the load 4.

Since the smoothing capacitor 2 needs to be charged to the rated voltage before operating the inverter device 3, the smoothing capacitor 2 is charged through the rectifier 1 at the same time when the main power is turned on. However, if the inrush current is too large, the rectifier 1, Since the capacitor 2 and the like are damaged, it is charged with the current limited by the limiting resistor 6.

In normal operation, if the limiting resistor 6 is present, power loss will occur. Therefore, since it is necessary to bypass the resistor 6, the electromagnetic switch 5 short-circuits the limiting resistor 6.

[0006]

Since the conventional voltage type inverter device is configured as described above, the limiting resistor having a large rated voltage and rated current only for initial charging and the short circuiting resistor are used. However, there is a problem in that the entire device becomes expensive because the electromagnetic switch must be provided.

The present invention has been made to solve the above problems, and an object thereof is to obtain an initial charging circuit for a voltage-type inverter which is inexpensive even with a large current and a high voltage, and further shortens the charging time. The purpose is to facilitate the addition of the charging current control circuit.

[0008]

The initial charging circuit for a voltage source inverter according to the first aspect of the present invention uses a plurality of voltage source type inverters in which a DC voltage charged in a smoothing capacitor is input and AC power is converted by the inverter. A step-down insulating transformer having a secondary winding, a rectifier circuit connected to one secondary winding to charge the smoothing capacitor with a DC voltage, and a current connected to another secondary winding to limit the primary current. And a limiting element.

Further, the initial charging circuit of the voltage source inverter according to the second aspect of the present invention inputs a DC voltage charged in a smoothing capacitor and converts AC power by the inverter so that a plurality of secondary windings are provided. It has a step-down isolation transformer, a rectifier circuit connected to one secondary winding to charge the smoothing capacitor with a DC voltage, and a constant current circuit connected to another secondary winding to stabilize the primary current. It is a thing.

[0010]

According to the first aspect of the present invention, the rectifier connected to the secondary side of the insulating transformer has a low voltage by limiting the primary current of the insulating transformer that supplies the charging voltage to the smoothing capacitor with the current limiting element. The DC voltage can be charged to the smoothing capacitor. According to the second aspect of the invention, the smoothing capacitor stabilizes the primary current of the insulating transformer by the constant current control circuit, so that the smoothing capacitor has a voltage across the capacitor and a charging rectifier connected to the secondary side. Since a constant charging current always flows regardless of the difference between the charging output and the charging output, the charging of the capacitor is completed quickly.

[0011]

EXAMPLES Example 1. FIG. 1 is a circuit diagram showing an embodiment of the present invention, in which 1 to 4 are completely the same as those of a conventional device, 5 is an electromagnetic switch for supplying control power, 7 is an insulating transformer, and 8 is charging. Rectifier, 9 is an insulating transformer connected in series with the charging circuit, and 6 is a current limiting resistor.

Next, in operating the inverter for explaining the operation of the present embodiment according to the above-mentioned structure, first, the electromagnetic switch 5 is closed and the insulating transformers 7 and 9 are used to initially charge the smoothing capacitor 2. Voltage is applied to. At this time, since the current limiting resistor 6 is connected to the secondary side of the insulating transformer 9, a momentary large current does not flow through the charging rectifier 8 connected to the insulating transformer 7, and the charging rectifier 8 is at a low voltage. A current gradually flows into the smoothing capacitor 2 and is charged.

Example 2. In FIG. 1, the insulating transformer 9 for the limiting circuit is provided, but if the resistor 6 can be manufactured to have appropriate voltage and current values for the control power source, then 9
Even if the resistor 6 is omitted and the resistor 6 is directly connected to the insulating transformer 7, the same effect as that of the above embodiment can be obtained.

Example 3. FIG. 2 shows an initial charging circuit for an inverter according to an embodiment of the second invention. In this circuit configuration, the constant current control circuit 10 is connected in series with the limiting resistor 6, and by incorporating the constant current control circuit 10, the currents flowing through the primary sides of the transformers 7 and 9 become constant, so that The charging current flowing on the secondary side is also constant. That is, in the circuit configuration shown in the first aspect of the present invention, when the smoothing capacitor 2 is charged more and the difference between the terminal voltage of the capacitor 2 and the output voltage of the rectifier 3 decreases, the charging current decreases. Therefore, it takes time for the smoothing capacitor 2 to complete charging.

However, with the circuit shown in FIG.
Since the constant current control circuit 10 controls so that a constant current always flows through the primary side of the insulating transformer, the charging current flowing through the secondary side of the insulating transformer 7 also becomes constant. Therefore, according to FIG. 2, charging can be completed 3 to 4 times faster than in the case of FIG. 1, and the maximum voltage of the constant current circuit is optimally designed by selecting the secondary voltage of the transformer 9. You can do it.

[0016]

According to the first aspect of the invention, the charging power for initially charging the smoothing capacitor for supplying the DC voltage to the inverter device is supplied from the separate power supply circuit, and the charging power is limited to an arbitrary value. Therefore, even when the smoothing capacitor has a large initial charging power, it is possible to configure the initial charging circuit with inexpensive components having a low withstand voltage rating. Further, according to the second aspect of the present invention, the constant current control circuit is provided at the output of the initial charging power supply circuit for initially charging the smoothing capacitor so that a stable charging current can always flow through the smoothing capacitor. In addition to the effect of the invention described above, there is an effect that charging of the smoothing capacitor is completed early.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the first invention.

FIG. 2 is a circuit diagram showing an embodiment of the second invention.

FIG. 3 is a conventional initial charging circuit diagram.

[Explanation of symbols]

 1 Rectifier for main power supply 2 Smoothing capacitor 3 Inverter device 4 Load device 5 Electromagnetic switch 6 Limiting resistor 7 Insulation transformer 8 Charging rectifier 9 Insulation transformer 10 Constant current control circuit

[Procedure amendment]

[Submission date] November 8, 1991

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction content]

[0008]

SUMMARY OF THE INVENTION The initial charging circuit of the voltage type inverter according to the first invention, an input DC voltage charged in the smoothing capacitor, the voltage source inverter for AC power converted by the inverter, two an insulating transformer step-down with secondary winding of one of the insulating Trang
A rectifier circuit connected to the scan of the secondary winding to charge the DC voltage to the smoothing capacitor, in which a current limiting element for limiting the primary current is connected to the other of the insulating transformer secondary winding.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction content]

Further, the initial charging circuit of the voltage type inverter according to the second aspect of the present invention is such that the DC voltage charged in the smoothing capacitor is input, and the secondary voltage of the voltage type intor for converting the AC power by the inverter has two secondary windings. an insulating transformer step-down having a rectifier circuit for charging the one insulation is connected to the transformer secondary winding DC voltage to the smoothing capacitor, the primary current is connected to the other of the insulating transformer secondary winding stable It is equipped with a constant current circuit that changes.

Claims (2)

[Claims] 1. In a voltage source inverter, which receives a DC voltage charged in a smoothing capacitor as input and converts AC power by an inverter, a step-down insulating transformer having a plurality of secondary windings and one of the secondary windings. An initial charging circuit for a voltage source inverter, comprising: a rectifying circuit connected to charge the smoothing capacitor with a DC voltage; and a current limiting element connected to another secondary winding to limit a primary current. 2. A voltage source inverter for inputting a DC voltage charged in a smoothing capacitor and converting AC power by an inverter, wherein a step-down insulating transformer having a plurality of secondary windings and one secondary winding are provided. An initial charging circuit for a voltage source inverter, comprising: a rectifier circuit connected to charge the smoothing capacitor with a DC voltage; and a constant current circuit connected to another secondary winding to stabilize a primary current.